Atomic Scala Summary 2 Exercise 8

gistfile1.scala

class Cell {
  var entry = ' '
  def set(e:Char):String = {
    if(entry==' ' && (e=='X' || e=='O')) {
      entry = e
      "successful move"
    } else
      "invalid move"
  }
}

class Grid {
  val cells = Vector(
    Vector(new Cell, new Cell, new Cell),
    Vector(new Cell, new Cell, new Cell),
    Vector(new Cell, new Cell, new Cell)
  )
  def play(e:Char, x:Int, y:Int):String = {
    if(x < 0 || x > 2 || y < 0 || y > 2)
      "invalid move"
    else {
      val move = cells(x)(y).set(e)
      if (winner) {
        println("We have a winner! :)")
      } else if (cells.forall(_.forall(_.entry != ' '))) {
        println("We have a draw! :(")
      }
      move
    }
  }

  def winner(): Boolean = {
    def winnerLine(line: Seq[Cell]): Boolean =
      line.forall(_.entry == 'X') || line.forall(_.entry == 'O')
  
    val range: Range = (0 until cells.size)
    val transposition: Seq[Seq[Cell]] = (0 to 2).map { i =>
      (0 to 2).map { j => cells(j)(i) }
    }
    val diagonalLeft = (0 to 2).map { i => cells(i)(i) }
    val diagonalRight = (0 to 2).map { i => cells(i)(cells.size - i - 1) }
    cells.exists(winnerLine) || transposition.exists(winnerLine) ||
      winnerLine(diagonalLeft) || winnerLine(diagonalRight)
  }
}

val grid = new Grid
grid.play('X', 1, 1)
grid.play('O', 1, 2)
grid.play('X', 2, 1)
grid.play('O', 2, 2)
grid.play('X', 0, 1)